High gain antenna reflectors have been deployed into space for several decades. The configurations of such reflectors have varied widely as material science has developed and as the sophistication of technology and scientific needs have increased.
Large diameter antenna reflectors pose particular problems during all phases of their existence, whether it is assembly, stowage, launch, deployment and/or usage. Double-curved, rigid surfaces which are sturdy when in a deployed position cannot be easily folded for storage. Often, reflectors are stored a year or more in a folded, stowed position prior to deployment. In an attempt to meet this imposed combination of parameters, large reflectors sometimes have been segmented into petals so that these petals could be stowed in various overlapping configurations. However, the structure required in deploying such petals has tended to be rather complex and massive, thus reducing the practical feasibility of such structures. For this reason, dish-shaped antenna reflecting surfaces larger than those that can be designed with petals typically employ some form of a compliant structure.
Responsive to the need for such a compliant structure rib and mesh designs have been supplied and utilized. A network of tensioned radial and circumferential chords divides the mesh into substantially flat facets. The effect on the reflector performance caused by the difference in shape between these flat facets and the true parabolic surface is referred to as the faceting error. Prior art mesh reflector designs require the use of numerous facets because the circumferential and angular spacing between the ribs and the mesh attachment locations are not optimized to minimize the faceting error.
Other antenna designs typically include a center post about which the petals are configured, much like an umbrella configuration. This also affects the reflective quality of the resulting surface, because the center portion typically is the point of optimum reflectance, which is often blocked by the center post. Thus, it is desirable to have a structure that is deployable from a compact, stored position to an open dish-shaped position without center post blockage.
More recently, many rigid antenna reflectors have been constructed from graphite fiber reinforced, plastic materials (GFRP). Such materials may satisfy the requirements for space technology and contour accuracy and, therefore, high performance antenna systems. However, power and performance of rigid antennas are limited, owing to the size of the payload space in a launch vehicle. Very large completely rigid antennas are highly impractical to launch into space, hence the requirements for practical purposes can be satisfied only when the antenna is of a collapsible and foldable construction.
At present, antenna reflectors of the collapsible and foldable variety are of two design types. One type is a grid or mesh-type reflector that is folded like an umbrella. The other type includes foldable rigid and hinged petal members. Antennas of the second type are available in a variety of configurations, some of which are disadvantaged by the requirement for an excessive number of joints and segment pieces which, owing to the particular folding and collapsing construction, are of different shape and size. Also, the larger the number of hinges and segments, the more complex will be the deployment mechanism and its operation. Any added weight also is a disadvantage relative to a satellite system.
For a given paraboloid reflector diameter, the number of ribs used determines the width of each mesh singly-curved gore. Thus, more ribs result in more and narrower mesh gores, with each narrower gore being a better approximation of the ideal paraboloid shaped gore.
While the existing paraboloid reflectors are satisfactory to some degree, they have several inherent disadvantages which detract from their usefulness. Among the foremost of these disadvantages are excessive weight, excessive stowage volume requirements, excessive cost and complexity, inadequate surface accuracy, and inadequate deployment reliability.